Telephony.



E. R. CORWIN.

TELEPHONY.-

APPLICATlON FILED APR.5.1913.

1,173,772., Patented Feb. 29,1916.

INVENTUR ELMER R: CORWIN.

WITNESSE Amwcar es.

ELMER R. COEEYIN,.GI" CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,TO FRANK B. CQUK GOMPANY. OF CHICAGO, ILLINOIS, A CORIORATION OFILLINOIS.

TELEPHONY.

Specification of Letters Patent.

Patented net. as, rare.

Application filed April 5; 1913. Serial No. 759,018.-

Chicago, in the county of Gook and State of Illinois, have invented acertain new and useful Improvement in Telephony, of which the followingis a full, clear, concise, and exact description, reference being had tothe accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems and has for one ofits objects the provision of devices for interchangeably connecting idlecalling line extensions with calling lines, such devices continuing inoperation until they have effected connection between idle calling lineextensions and calling lines.

My invention has for another of its objects the provision of means forreducing the number of motor devices in operation at one time, therebeing means for bringing an idle motor device into operation when apreviously operating motor device has been brought to rest after havingperc formed its function of extending the calling line, and this featureof the invention is broadly claimed irrespective of the manner and meanswhereby the motor devices effect changes in or addition to the telephonelines at the exchange and while the motor devices preferably do notcause the bodily travel of contacts the invention, in all of itscharacteristics, is not to be thus limited.

In the preferred embodiment of my invention the link connectors areequipped with the motor devices that are then preferably individualthereto and by means of this feature of my invention the telephone linesmay be stripped clear of line magnets and relays. In this embodiment ofthe invention the lines of the system are divided into groups, say ofone hundred lines per group, and enough link connectors are assigned tosuch group to equal the maximum traffic to be borne, ten link connectorsper group.

The invcntion, as shown in the embodiment herein disclosed, is employedin connection with a so-called semi-automatic system in which the linkconnectors are automatically connected with calling lines and areconnected with called lines by operator controlled means such asterminal plugs ratchet wheel 9 operated thereby.

provided for the link connectors and spring jacks supplied to thetelephone lines. The invention is, however, not to be restricted to sucha system. i

There are other features of my invention and the various features of theinvention will be further explained by reference to the accompanyingdrawing showing the pre-,

ferred embodiment thereof and in v'vhich- I Figure 1 diagrammaticallyillustrates telephone lines extending from substations to an exchange,all equipped in accordance with the invention; and Fig. isa viewillustrating a motor device.

The equipment at stations 120 and 190 is illustrated as including atelephone switch hook 1 having a normal contact for completing-atelephone line bridge including-a call bell 2 and an alternate contactfor completing a telephone line bridge that includes a telephonereceiver 3 and a telephone transmitter 1 this latter bridge being closedwhen the switch hook is free of the telephone receiver and the bellbridge being closed when the switch hook supports the receiver. Thesignal bells are preferably of high resistance, say five thousand ohms,the system of my present invention, according to its present embodiment,enabling me to dispense with the condensers in the bell bridges. Thetelephone lines are provided with terminals 5, 6 at the exchange, therebeing ten pairs of such terminals per line, as there are ten motordevices for each. group of one hundred lines in the example chosen forillustration When the lines are to be adapted for, connection withcalling plugs they are also provided with springjacks 7 multiplied inthe various sections of the switchboard. The line terminals 5 and 6 areprovided each with a complemental contact, similar contacts of the linesof a group being in multiple connection, such connection beingunderstood, though there are but two lines illustrated in the drawing.Similarly positioned contacts in each group are multipled. Each motordevice is shown as including a motor magnet 8 and a Each ratchet wheelis in actuating relation to an arm- 10. This arm carries a steel roller11 adapted to ride over the contact springs 5 and in riding over suchsprings to depress the same to bring them into engagement with theircomplemental contacts at which times the contact springs 6 are alsobropiglat into engagement with their complemental: contacts owing to themechanical couplings which intervene between the free ends of thesprings 5 and (3. The roller 11 of each motor rides over the contactsprings 5 of all of the lines of the group of one hundred lines to whichthe motor pertains.

\Vhen a call is initiated the high resistance bell bridge between thesides of the calling line is replaced by the low resistance telephonebridge so that the calling line is adapted to the transmission ofcurrent in sufiicient volume to operate the equipment to be describedthat will stop the operation of the motor, which has depressed thecontacts 5 and 3 of the calling line, so as to maintain contacts 5 and(3 in connection with their complemental contacts. \Vhen the contacts 5and 3 are thus maintained in connection with their con'iplementalcontacts another and previously idle motor device is set into operationso as to enable it to maintain the contacts 5, (S of another callingline in engagement with their complemental contacts whereupon anotherand previously idle motor device is brought into 7 service.

Any suitable means may be employed for the motor device, that shownincluding the motor magnet 8 included in a circuit that contains acircuit interrupter 12 for intermittently energizing said motor magnetto cause it to operate the ratchet wheel 9 which is provided with onehundred teeth, one tooth per line, each operation of the motor magnetremoving the roller 11 from engagementwith one contact spring intoengagement with the next. The circuitfor the motor magnet includes theinterrupter 12, said motor magnet, the normal contact of the armatureswitch of relay 13, the left hand armature switch of energized relay14,'and the grounded battery or source of current 15,this source ofcurrent being common to but normally dissociated from the telephonelines and the link connectors. This source of current is preferably ofsuch a nature that it may be retained in circuit relation with connectedtelephone lines so as to supply the transmitters at the connectedstations with direct ga u'rent, though the invention is not tobe'iimited to the functions which the common source of currentperforms.Each time the contacts 5 and 6 of each of the hundred lines of a groupare brought into engagement with their complemental contacts a circuitis established which 'is traceable from the grounded batterv15, thewinding of relay 13, the intermediate armature switch of relay 14and-its contact, the depressed contact 6, the contact complemental tothe contact 6, both sides of the line having such contact 6, the contact5 of this line, the contact hooks the line-circuits are of too high re-I sistance to cause the relays 13 to be energized owing to theresistance of the bells 2. lVhen, however, a call has been initiated,

the telephone bridge at the calling station joins the line sides througha path of sufliciently low resistancetopermit sufficient How of batterycurrent through the relay 1.3 to cause this relay to be energizedthereby to open the circuit of the motor magnet at the normal contact ofthe armature switch of the relay 1?) to prevent further operation ofthis motorrmagnet whereby the contacts 5 and 6 are maintained depressedand in connection with their complemental contacts. The relay 13 isdesirably of five thousand ohms resistance and the impedance device 16is desirably of fivethousand ohms resistance.

When the relay 13 is energized its armature switch engages its alternatecontact to establish a circuit traceable from the grounded battery 15,the left hand armature switch of relay 14 and its contact, the-armatureswitch of relay 13 and its alternate contact. the winding of relay 17,the contact 6 pertaining to the calling line, the contact complementalto this contact, both sides of the calling line, the contact 5 of thecalling line, the contact complemental to the contact 5, the impedance16, the right hand armature switch of relay 1 1 and its contact, toground. When relay 17 is energized a circuit is established traceablefrom the grounded battery 15, through the two middle contacts of anoperators switching mechanism 18, the left hand armature switch of relay17 and its alternate contact, the winding of relay 17, the contact 6 ofthe calling line, the contact complemental thereto, both sides of thecalling line, the contact 5 of the calling line and the contactcomplemental thereto. the relay 19, the right hand armature switch ofrelay 17 and one of its contacts, to ground, the circuit just tracedconstituting a holding circuit for the relay 17. When the relay 17 isenergized a holding circuit is established at its right hand armatureswitch for the relay 13, which holding circuit is traceable from thegrounded battery 15, the winding of relay 13, the right hand armatureswitch of relay 17 and one of its contacts, to ground. A.

third circuit is established at the right hand armature switch of relay17 which is traceable t'rom the grounded battery 15, the motor magnet20, the wiper 21 fixedly carried upon the shaft of a ratchet wheel 22, awaiting contact engaged by the wiper 21, the right hand armature switchof relay 17 and one of its contacts, to ground. .The motor is understoodthat each motor element89 has a relay 1'? individual thereto. When therelay 19 was energized it opened a circuit at its left hand armatureswitch for the relay 14, the circuit for this relay 1% having beenpreviously established when the motor magnet 20 was operated to bringthe wiper 21 into engagement with a waiting contact that was thenassociated with the relay 17 when this relay was-unenergized. Thecircuit for the relay 1 1 is traceable from thegro'unded battery 15, themiddle contacts of the oper-' ators switching mechanism 18 (there beingone switching mechanism 18 for each motor device 89) the left handarmature switch of relay 19, when dee'nergized, and its contact, thewinding of relay 1%, a wiper fixed upon the shaft of the ratchet wheel22 and the waiting contact individual to the relay 14, to ground. Themaster switching mechanism comprising the elements 20., 21, 22 and 23 iscommon to each group of ten motor devices 8-9 and its relatively fixedwipers 21 and 23 have ten pairs of waiting contacts, in the exampleunder illustration,

the ten waiting contacts of the wiper 21 each being individual to adistinct relay 17 and therefore each individual to a distinct motor 8 9as each motor 89 has a relay 17 individual thereto, while the tenwaiting contacts-of the wiper 23 are each individual to a distinct relay14 and therefore each individual-to a distinct motor 89, as each motor 89' has a relay 14 individual thereto.

By the organization described it' will be seen that as each motor 89 hasbecome arrested, owing-to the establishment of a low resistancetelephone bridge at a calling line station, in order to maintain theline contacts 5, '6 in engagement with their complemental contacts, themagnet 17 individual to such motor 89 becomes energlzed so to enable themaster switching mechanism ,20 23 to energize the relay 14: individualto some other but then idle motor 89 to bring this'other motor intoconstant operation, itself to be arrested whenits roller 11 depresses apair of contacts 5, 6; of a calling I line to join it with the linkconnector at such newly operating motor, the employment of 1 mined totheeirclusion. of its idle companion this link connector'newly selected bythe master selector switch-being thus predeterin the same group. Whenthe calling subscriber (station 120) restores his telephone the waitingcontact individual to this particular relay 14 associated with thepreviously calling line 120, this relay 1a is energized so that themotor 89 is brought into operation whereby the roller 11 may pass overthe contacts 5 until it engages a contact 5" pertaining to a new callingline, wi h results previously described.

When one motor 89 has been brought to rest in association with a callingline in the manner previously described a second or some other motor inthe same group will bring its rollers 11 into temporary depressinengagement with a contact 5 in multiple with the contact 5 of saidcalling line, this temporary depressing engagement occurring during thesweep of the arm 10 This second or other motor will not be ar-. restedwhen in engagement with the said multiply related contact 5 owing to thecomparative resistance of the relays 17,, 19 which are preferably of twohundred fifty ohms resistance each and the relay 13 and impedance 16each preferably of five thousand ohms resistance, the battery 15 beingpreferably of fifty volts. With this arrangement sufiicientcurrent isdiverted from the element 13 of the second or other motor through therelays 17 and 19 connected with the calling line to prevent theenergization of relay'13 pertaining to such second or other motorwhereby such other motor is not arrested with its roller ll incontinuing engagement with a contact 5 in multiple with the contact 5that is being maintained depressed by the roller 11 of the first motor8-9 that is associated with such calling line.

The link connector forjoining the'callin'g line with a called lineincludes a connecting plug 24 having tip and sleeve strands, though theinvention is not to be limited to such a connecting terminal. A relay25, preferably of two hundred fifty ohms resistance, is connected withthe tip strand of the plug Fla there being a. condenser 26 intel-posedbetween the terminals of the relays 19 and 25. I When the plug 24 isinserted in the jack of a called line and the called subscriber hasresponded suflicient current is diverted from the relay 13 of anoperating motor 8-9 to prevent such operating motor from becomingarrested with its roller 11 in continuing depressing engagement with thecontact 5 of thecalled line whose station has responded. F or reasonspreviously explained, an operating motor 8-9 will not become arrested inassociation with a desired linethat has been plugged into owing to theabsence of the low resistance telephone bridge at't'he called station,this prior to the ringing of the bell at the de sired station. A ringingkey 27 serves to bridge a ringing generator 28 between the tip andsleeve strands of the plug 21 to opcrate the bell 2 at the desiredstation. When this key is depressed the nose 29 of the lower armature ofa relay 30 engages the notch 31 in the key, shank so as to hold said keyin its ringing position. The relay 30, which may be of twenty ohmsresistance, is in series with the generator 28, the resistance of thesignal hell 2 cutting down the ringing current sufficiently to preventthe relay 30 from being energized while the bell 2 is in circuit. Whenthe called subscriber responds the low resistance telephone bridge atthe called station will permit a sufficient increase in the flow ofcurrent from the generator 28 through the relay 30 to energize the relay30 to attract its lowerarmature to withdraw the armature nose from thecontact. the winding of relay 32, the right hand armature switch ofrelay 19 and its contact, the two middle contacts of the operator switch18 to the grounded battery 15. f

The top and bottom armature switches of relay 32 thereupon establishcontinuations of the tip and sleeve strands of theplug 24. The middlearmature switch of the'relay 32 establishes a locking circuit for itselftraceable from the grounded contact of this middle armature switch, saidarmature switch,

the winding of relay 32, thence to the battery 15 by way of therighthand armature switch of the energized relay 19. 'While the ringingkey 27 was depressed a circuit was established traceable from thegrounded impedance coil 33 of, say, two hundred fifty ohms resistance,the two contacts of the lower spring of the ringing key 3% and a portionof this spring, the relay of. say, two hundred fifty ohms resistance,thence to the grounded battery 15 by way of the right hand armatureswitch of relay 19. Thus potential is placed upon the thimbles of themultiple jacks in connection with the called line and also upon thecontacts 6 of the called line. The potential placed upon the thimbles isfurnished by a connection traceable from the grounded battery 15, themiddle pair of contacts of the key 18, the right hand armature switch ofthe relay 19 ,and its contact, the relay 35, the ringing switchspring 34and one of its conjack of the busy line, thence to the other thimbles ofthis line. It should be observed in passing that the spring 3% engagesits contacts before the companion ringing spring engages its contactswhen the plunger 27 is depressed.

1V hen a desired line is tested the test circuit is continued from thethimble of the tested jack of the desired line through the tip of thetesting plug 24, the upper armature switch of relay 32 and the contactnormally engaged thereby, the upper spring of the testing operatorslistening key 36 and the two contacts then engaged thereby, to thegrounded connection provided for the operators receiver. The potentialupon thethimbles of' the calling lines is established for testingpurposes by way of a connection traceable from the grounded battery15,the

winding of relay 13 associated with the calling line, the middlearmature switch of re-' lay l-l, the contact complemental to the contactG of the calling line, the contact 6 of the, calling line, thence to thethimbles of the calling line jacks.

To prevent any motor 8-9 from remaining in continuing engagement with acontact 5 of a line over which ringing current is being passed effectivecurrent from battery 15 is prevented from flowing through the coil 13 bya shunt established for the battery current traceable from the groundedbattery 15, the middle contact of the key 18, the right hand armatureswitch of the relay 19, the relay 35, the two contacts engaged by theringing spring 34, the impedance 33, to ground. If the calling partyrestores his telephone before the called party responds, relay 35-willbe deenergized owing to the breaking of the circuit thereof at the righthand armature switch of relay 19 whereupon circuit for relay 30 isestablished at the armature switch of relay 35 to withdraw the lowerarmature of relay 30 from engagement with the ringing key '27 thereby hto remove the ringing generator 28 from circuit with the called line.The tip and sleeve strands leading to the plug 24 are,

phone lines in the group of one hundred.

Thus the calling subscriber. in addition to causing the operations whichhave been de-, scribed also. in the embodiment of the invention hereinshown, automatically extends his telephone line into connection with anoperator controlled terminal 21, though. this invention is not to bethus restricted. Then the answering end of a link connector has thusbecome automatically connected with the calling line and the connectingend of the link connector hasbeen manually connected with a called lineby the operator, the calling and called telephone lines are placed inconnection and are in telephonic connection when the receivers at bothstations are free of their switch hooks. When the subscribers restoretheir telephones upon their switch hooks when through theirconversation, the paths for current from the battery through thetelephone lines are broken owing to the breakage of the low resistancetelephone bridges at the stations whereby the relay 17 is deenergized toclear the line and link of battery, this relay remaining energized aslong as either telephone is free of its switch hook. When the relay 17is de'e'nergized the relay 19 is deenergized and the relay 32 is alsodeenergized to-restore its armature switches to normal, the calling andcalled lines beinga-gain separated at the top and bottom armatureswitches of relay 32. By clearing the link and lines of battery whenboth telephones of connected stations are restored to their switchhooks, the roller 11 may remain in depressing engagement with thecontact 5 of the calling line and, owing to the then decnergizedcondition of the relay 32, the plug 24 may remain in the jack of thecalled line, no battery being furnished to the particular link until themotor magnet 20 again brings its wiper 23 into connection with thewaiting contact individual to the relay 14 of this link so that anothersubscriber may employ this link for resuming his connection with theother subscriber until the relay 14 of this link has thus becomeconnected with the wiper 23 of the master switch. As a result thetraffic in the system is not interfered with even though the broken linkconnectors remain in connection with lines which they previously joined.The relay 19 is within the control of the calling subscriber and therelay 25 is within the control of the called subscriber owing to thepresence of the condenser 26. The right hand armature switches of theserelays are made to operate display devices so that these relays areconstituted supervisory relays or signals. When the relay 19 1Sinitially operated upon the initiation of. a call by acalling subscriberits right hand armature switch operates the signal device and theoperator, in response to such signal, depresses her listening key 36 tobridge her telephone set between the sides of the link connectorautomatically selected by the calling subscriber to ascertain the numberof the line wanted, though'it is tobe understood that the invention isnot to be limited to a system in which the signal "device 19 is thusoperated to attract the attention of the operator.

Each link connector has an operato-rs key 18 provided with three pairsof contacts and a switch-lever in one position separating the contactsof onepair and closing the contacts of another pair, and in anotherposition oining the contacts of the remaining pair.

.When the c'pntacts of the middle pair of a. key 18 are'separated therelay 14 individual thereto has its circuit broken thereat. Each key 18has aloft hand pair of contacts which, when the key is operated toseparate the middle pair of contacts, establishes a circuit through themotor magnet 20 to prevent the mctor magnet from being tied up with alink connector that is put out of service by the operator. The ten linkconators employed are in proportion to the trafiic, the switches 18 ateach unattended operators position being thrown, as hitherto described,to prevent calls from being received at such unattended positions. Whenthe right hand contacts of any key 18 are engaged the operator may calla line and, upon depressing her-key 36, may conversewith the station shecalls. The closure of the right hand contacts of the key 18 establishesa circuit for the relay 17 (by way of the operators telephone set) toenable the operator to manipulate her ringing key 27 and secureconnection with a line by means of the associate ping 24. Theenergization of. the relay 1'? thus ettected by the operator preventsthe associate link connectcrfrom being appropriated by a calling line.In addition to the other advantages which have been recited the normalabsence of battery upon the telephone lines and link connectors is animportant factor, as will be apparent without further comment.Condensers 13 16 serve to receive discharges occurring when rollers 11pass contacts of telephone lines.

\Vhile I have herein shown the contacts 5, 6 as being individual to andpermanently connected with the telephone lines, it is ob vious that theinvention is not to be restricted to such a eiaracteristic in all of itsembodiments. In the organization described the wheels 11-are intraveling relation to the contacts 5 and 6 and the invention disclosesmotor mechanism whereby the wheels 11 are themselves caused to,travelwhile the contacts 5 and 6 and the contacts complemental to contacts 5and 6 have stationary mountings. I do not limit myself to this mechanismfor securingrelative travel between the contacts 5 and 6 and the contactactuators 11,.

\Vhile I have herein shown and particularly described the preferredembodiment of my invention I do not wish to be limited to the precisedetails of construction. and cir cnit arrangement shown as changes mayreadily be made withoutdeparting from the spirit of my invention. but

Having thus described my invention I claim as new and desire to secureby IJQt" ters Patent the following:

1. A telephone exchange system including telephcne lines extending fromtelephone staticns to an exchange where these telephcne lines areprovided with circuit controlling crntacts; contacts complemental to theforegoing contacts; motor devices for changing the relation of thesecontacts; master switches for bringing the motor devices into operation;and mechanism governed by station apparatus of calling lines for causingthe operation of the, motor devices to cease upcn changing therelationship of the contacts of calling lines with their complementalcontacts and for tljereupon causing the operation of the master switchto bring another motor device into operation.

2. A telephone exchange system including telephone lines extending fromtelephone stations to an exchange; switching devices for extending theline circuits; motor devices for operating the switching devices; masterswitches for setting the motor deices into operation; and means governedby apparatus at stations of calling lines for causing the nn'tor devicesto cease operation upon operating the switching devices to extendcalling line circuits and for thereupon operating the master switch tobring an idle motor device into operation.

3. A telephone exchange system including .teleihcne lines extendin fromtelcihone stations to an exchange; link conductors for uniting lines inconversation; switching de vices lor ]()lll1llg link connectors \Htllcalling lines: motor devices for operating the switching devices; masterswitches for setting the mctor devices into operation; and

means governed by apparatus at stations of calling lines for causing themotor devices to cease operation upon operating the switching devices toextend calling lines into connection with link connectors and forthereupon operating the master switch to :bring an idle motor deviceinto operation.

4. A telephone exchange system including telephone lines extending fromtelephone stations to an exchange where these telephone lines areprovided with circuit controlling contacts; contacts complemental to theforegoing contacts; motor devices for changing the relation of thesecontacts; master switches for bringing the motor devices into operation;mcchanisn'i governed by station apparatus of calling lines. for causingthe operation of the motor devices to cease upon changing therelationship of the contacts of calling lines with their complementalcontacts and for thereupon causing the operation of the master switch tobring another motor device into operation; and means whereby the masterswitch is prevented from bringing the motors that have been arrested bycalling lines again into operation while the calling lines arein circuitwith calling station telephones.

A telephone exchange system lncluding from bringing the motor devicesthat have been arrested by calling lines again into operation while thecalling lines are in cm cuit with calling station telephones.

(i. A telephone exchange system including telephone lines extending fromtelephone stations to an exchange; link connectors for uniting lines inconversation; switching devices tor joining link connectors with callinglines; motor devices for 'operating the switching devices; master.switches for setting the motor devices into operation; means governed byapparatus at stations of calling lines for causing the motor devices tocease operation upon operating the switching de- \'ices to extendcalling lines into connection with link connectors and for thereuponoperating the master switch to bring an idle motor device intooperation; and means whereby the master switch is prevented fromln'inging the motor devices that have been arrested by calling linesagain into operation while the calling lines are in circuit with callingstation tele 'il'lones.

7. A telephone exchange system including telephone lines extcmling fromtelephone stations to an exchange where these telc phone lines areprovided with circuit controlling contacts; contacts complemental to theforegoing contacts; motor devices for changing the relation of theseconlacts and common to a plurality of sets thereof; mas ter switchesfor. bringing the motordevices into operation; and mechanism governed bystation. apparatus of calling lines for causing the operation of themotor devices to cease upon changing the relationship of the contacts ofcalling lines with their complemental contacts and for thereuponcausing.

tion apparatm the operation of the master switch to bring another motordevice into operation.

8. A telephone exchange system including telephone lines extending fromtelephone stations to an exchange; switching devices for extending theline circuits; motor devices for operating the switching devices andcommon a plurality of such switching devices; master switches forsetting the motor devices into operation; and means governed loyapparatus at stations of calling lines for causing the motor devices tocease operation upon operating. the switching dc vices to extend callingline circuits and for thereupon operating the master switch to bring anidle motor device into operation.'

T. A telephone exchange system includtelephcne lines extending fromtele- 1 nc stations to an exchange where these denhone lines areprovided with circuit controllir contacts; contacts complemental the i"cing contacts; motor devices lchanging ihe relation of th ise contactscommon to a plurality of sets thereof; master switches bringing dev nemotor into operatic mechanism governed by s calling lines for car theoperation or" the motor devices to cease anon changing the relationshipof the con- 1 acts of calling lines with their complemenril contacts andfor thereuponcausing the operation of the master switch to bring another motor def-v into operation; and means when master switch is pre--vented from l inning the motor devices that have been arrested bycalling lines again the callii lines'arc in to operation will} circuitwith calling ll. A telephone exchange system including telephone linesextending from phone stations to an exchange; 'sYv A inn" devices forextending the line circuits; motor devices for operating the switchingdcvices and common to a plurality of such switching devices; masterswitches for settin; the motor devices into operation; means govi ned byapparatus at stat-ions of calling lines for causing the motor devices tocease operation upon operating the switching de-' vices to extendcalling line circuits and for thereupon operating the master switch tobring an idle motor device into operation;

and means whereby the master switch is pre ing telephone lines extendingfrom telephone stations to an exchange; link connectors for unitinglines in conversation; switching devices for joining link connectorswith calling lines; motor devices for operating the switching devicesand common to a plurality of such switching devices; master switches forsetting the motor devices into operation; means governed by apparatus atstations of calling lines for causing the motor devices to ceaseoperation upon operating the switching devices to extend calling linesinto connection with link connectors and for thereupon operating themaster switch to bring" an idle motor device into operation; and meanswhereby the master switch is prevented from bringing the motor devicesthat been arrested by callin i to operation while r p hone sta devicestor devices vices; aster switches Il devices into operation; and meansgoverned ins at stations of calling lines for the motor devices. tocease operpon operating the switching devices d calling line c rcuitsand for thereo aerating the motor de" siting the motor ing circuits fortacts whose circuit relations are governed by the master switches whichare individual to said relays ablishing the relay circuits to cats? shthe operating cirl and operating ii'cuit i Us to:

s est-ahlis? d by calling line nose whereby the m0- cease their operatinc ,l in with calling tending terminals to connect lines with lineextensions and operating normally to effect engagen'ient between lineterminals and line extending terminals; and operator controlledelectromagnetic means for joining the sections ofline extensions takenfor use.

15. A telephone system having lines extending from stations to anexchange; calling line extensions, each complete line extension beingdivided into permanently serially related normally separated sections;calling line extending devices having calling line extending terminals;means for effecting relative movement between line terminals and lineextending terminals to connect filling lines with calling lineextensions and operating normally to effect engagement between lineterminals and calling line extending terminals, and operator controlledelectro-magmetic means for joining the sections of the line extensionstaken for use. I

In Witness whereof. I hereunto subscribe my name this thirty-first dayof March, A. D. 1913.

ELMER R. CORWIN.

\Vitnesses G. L. Canoe, E. L; \Vm'rn.

